An investigation of the self-assembly of neutral, interlaced, triple-stranded molecular braids
Journal
Chemistry - A European Journal
Journal Volume
12
Journal Issue
24
Pages
6281-6289
Date Issued
2006
Author(s)
Abstract
The synthesis and structures of six compounds prepared in two different systems have been explored with the purpose of isolating coordination polymers with interlaced triple-stranded molecular braid architectures. The dinuclear paddle-wheel units of [Cu2(maa)4·2H2O] can be rationally tuned to form three classes of isomorphous compounds, namely [Cu2(maa)4(bpp)] (1) (bpp= 1,3-bis(4-pyridyl)propane, Hmaa = 2-methylacrylic acid), [Cu3(maa)6(bpp) 2] (2), and[Cu4(maa)8(bpp)4(H 2O)2]·2H2O (3), with a bridging bpp ligand, at controlled ligand-to-metal molar ratios, and lead to three coordination polymers having similar one-dimensional characteristics but different mono- and dinuclear nodes. Compound 1, with a bpp:[Cu 2-(maa)4·2H2O] stoichiometry of 1:1, contains a zigzag chain containing dinuclear nodes, whereas polymer 2, with a bpp:[Cu2(maa)4·2H2O] stoichiometry of 1.5:1, also adopts the topology of a zigzag chain but with both mono- and dinuclear nodes. Compound 3, with a bpp:[Cu2(maa) 4·2H2O] stoichiometry of 2:1, contains a neutral, interlaced, triple-stranded molecular braid, which is interwoven by three single-stranded meso-helical chains that contain only a mononuclear node. With the three aromatic chelating terminal ligands 2,2′:6′,2″-terpyridine (tpy), 1,10-phen anthroline (phen), and di(2-pyridyl)amine (dpa) we have also prepared three neutral complexes containing the linear, rigid bridging ligand biphenyl-4,4′-dicarboxylate (bpdc), namely [Cd-(bpdc)(tpy)]·H2O (4), [Cu(bpdc)-(phen) 2]·4.25H2O (5), and [Cu(bpdc)-(dpa)] (6). An infinite meso-helix is formed initially in 4, and then three of these chains assemble into a triple-stranded braid similar to that of 3. Complexes 5 and 6 have a mononuclear and a looped dinuclear structure, respectively. Compounds 3 and 4 are unusual examples of triple-stranded molecular braid coordination frameworks based on different types of coligands. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.
Type
journal article